Diamond is a highest hardness substance among the substances existing on earth, and thus, a sintered body including diamond has been used as a material for a wear-resistant tool, a cutting tool and the like.
Japanese Patent Laying-Open No. 2003-292397 (PTD 1) discloses a diamond polycrystalline body which is a sintered body composed of diamond converted and sintered from a carbon substance of a graphite-type layered structure under ultrahigh pressure and ultrahigh temperature without addition of a sintering aid and a catalyst, wherein an average particle size of diamond is not larger than 100 nm and a purity is not lower than 99%. Japanese Patent Laying-Open No. 2003-292397 (PTD 1) also discloses a method for manufacturing the diamond polycrystalline body by direct conversion without addition of a sintering aid and a catalyst, by putting a non-diamond carbon substance into a pressure cell including indirectly heating means, and performing heating and pressing.
International Publication No. 2009/099130 (PTD 2) discloses a diamond polycrystalline body obtained by being converted and sintered from non-diamond-type carbon under ultrahigh pressure and ultrahigh temperature without addition of a sintering aid and a catalyst, wherein an average particle size of sintered diamond particles forming the diamond polycrystalline body is larger than 50 nm and smaller than 2500 nm, and a purity is not lower than 99%, and a D90 particle size of diamond is not larger than (average particle size+average particle size×0.9).
Japanese Patent Laying-Open No. 9-142933 (PTD 3) discloses a diamond sintered body including 0.1 to 30 volume % of a substance composed of oxide and/or oxycarbide and/or carbide of a rare-earth element, and the balance diamond.
Japanese Patent Laying-Open No. 2005-239472 (PTD 4) discloses a high-strength and high wear-resistant diamond sintered body including sintered diamond particles having an average particle size of not larger than 2 μm, and the balance a binder phase, wherein a content rate of the sintered diamond particles in the diamond sintered body is not lower than 80 volume % and not higher than 98 volume %, the binder phase includes cobalt and at least one or more types of elements selected from the group consisting of titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, and molybdenum, a content rate of cobalt in the binder phase is not lower than 50 mass % and lower than 99.5 mass %, a content rate of the at least one or more types of elements in the binder phase is not lower than 0.5 mass % and lower than 50 mass %, a part or all of the at least one or more types of elements selected from the group consisting of titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, and molybdenum is present as carbide particles having an average particle size of not larger than 0.8 μm, a structure of the carbide particles is discontinuous, and adjacent sintered diamond particles are coupled to each other.